Modeling the Neurological and Physiological Effects of Lactobacillus Rhamnosus on Adult Mice

Zainab Suleiman

Abstract

Probiotics are microorganisms that have beneficial properties for the host, and although probiotics have been used for generations to promote digestive health recent literature has suggested that these bacteria may provide more than just a localized effect at the level of the digestive track. Previous research demonstrated that mice consuming high doses of Lactobacillus rhamnosus had measurable differences compared to control mice in behavioral tests that measure stress and anxiety. The previous studies did not identify what aspects of the microbial cell provided the positive, probiotic effect so studies were initiated to identify whether this effect was due to direct interaction between the gut lining and the microbes or whether this effect was due to some factor produced by the microbes. To examine the probiotic effect a series of behavior tests that included an open field and forced swim test were performed on mice fed live L. rhamnosus, inactivated L. rhamnosus, cell lysates and L. rhamnosus conditioned media. Physiological factors including cortisol levels, fecal output and mass of each individual mouse were collected. It was hypothesized that mice that were administered live strains of the bacteria would show a significant decrease in anxiety and depressive behaviors. A trend appears in the open field test where mice fed inactive bacteria are the least responsive in each component of the open field test with the lysate samples approaching the group that received only media (control). The significance of this trend is unknown and suggests a molecule that is sensitive to heat and denaturation may play a role in the health benefits. The cortisol levels in the fecal samples are being analyzed and may provide insight into how this bacterial species plays a role in stress and clarify the open field data. If probiotics are found to be useful in decreasing stress like disorders, it could augment the current chemotherapeutic options.